The present invention relates to a radio communication analyzer having a function of testing the function of a radio unit and, more particularly, to a radio communication analyzer for testing the signal characteristics of a target signal (to be tested) obtained by phase modulation of a carrier wave with a digital data signal.
In order to effectively use communication lines, TDMA (Time Division Multiple Access) is used as a communication scheme between a base station and a radio unit as a mobile terminal, e.g., a car phone or a portable telephone, used in a mobile communication system.
As such TDMA schemes, PDC, PHS, GSM, and the like are used in practice. A burst signal having a signal interval T.sub.1 and a non-signal interval T.sub.2 set in one signal period T.sub.0 like the one shown in FIG. 3 is exchanged between a base station and each radio unit (substation).
In this burst signal, digital data to be transmitted, which consists of "1" or "0", is converted into a digital baseband signal (to be referred to as a digital data signal hereinafter) with a predetermined clock signal. Quadrature modulation of a high-frequency carrier is performed by using this digital data signal. The resultant signal is then inserted in the signal interval (burst interval) T.sub.1 of the burst signal.
In a radio communication analyzer that measures the signal transmitted from each radio unit to a base station to check whether it has signal characteristics complying with certain standards, the analyzer receives the burst signal output from the radio unit as a target signal, and measures various characteristics and precisions of the target signal.
The measurement items concerning characteristics and precisions to be measured in the conventional techniques roughly fall into the following three categories:
(a) measurement of inphase and quadrature components on a coordinate system to check whether a carrier is properly phase-modulated with a digital data signal (data on the I/Q coordinate system will be referred to as I/Q coordinate data, and measurement of such data will be referred to as I/Q coordinate data measurement);
(b) power measurement, e.g., measurement of the amplitude of a target signal; and
(c) frequency measurement of a target signal.
Note that I/Q coordinate data measurement includes measurement of modulation precision, frequency deviation, and the like, and power measurement includes measurement of antenna power deviation, carrier-off interval leakage power, ramp-up/ramp-down characteristics, and the like.
Frequency measurement includes measurement of occupied bandwidth, adjacent channel leakage power, and the like.
In general, measurement is mainly performed in the quadrature modulation (phase) domain (a), the amplitude domain (b), and the frequency domain (c) because of easy implementation of measuring devices.
According to a general technique of performing each of the above measurements in a radio communication analyzer, the analyzer is set in a measurement mode for one measurement category to measure the respective characteristics and precisions in the set measurement category.
More specifically, when, for example, the antenna power deviation, carrier-off interval leakage power, and ramp-up/ramp-down characteristics in the power measurement category are to be measured, a clock signal for a digital data signal is regenerated from a received target signal, and a burst start signal indicating the start of a burst interval is regenerated.
Signal acquisition positions for the target signal are specified by this clock signal, and the burst start position of the target signal is specified by the burst start signal.
Subsequently, the antenna power deviation during the burst interval (carrier-on interval), carrier-off interval leakage power indicating power during the burst-off interval (carrier-off interval), and burst rise/fall characteristics are calculated.
It is then checked whether the obtained characteristics meet the standards.
When measurement processing for the respective characteristics and precisions concerning the respective measurement items belonging to one measurement category is complete, the radio communication analyzer is set in a measurement mode for the next measurement category to start measurement of the respective characteristics and precisions in the set measurement category.
As described above, the measurement modes of the radio communication analyzer are sequentially switched to measure the respective characteristics and precisions in the respective measurement categories, as needed.
The following problems remain to be solved in the above radio communication analyzer.
In the respective measurement categories described above, precision and error measurements are independently performed. However, even characteristic measurement and precision measurement concerning different measurement categories sometimes include a common procedure for processing a target signal.
For example, the clock signal and the burst start signal must be detected in both the power measurement category and the I/Q coordinate data measurement category described above.
Every time the radio communication analyzer is switched to a mode corresponding to one of the above measurement categories, detection processing for the same clock signal and the same burst start signal must be executed, resulting in a deterioration in measurement efficiency.
Assume that the respective measurement items belonging to a plurality of measurement categories are to be executed. In this case, when the operator designates one measurement category, the respective characteristics and precisions in the designated measurement category are measured. When the measurement is complete, the measurement results are displayed on a display unit.
The operator then designates the next measurement category to execute measurement of the respective characteristics and precisions in the designated measurement category.
In this manner, the operator sequentially designates the respective measurement categories, and checks the measurement results on the display screen. That is, the operator must repeatedly execute such a series of complicated operations. The measurement efficiency may therefore greatly deteriorate.
In addition, since measurement is executed for the respective measurement categories on the basis of data of a target signal in different time zones, the measurement is performed for different target signals in effect. In the strict sense, since the respective measurement results are not obtained from the same target signal, the test results cannot be compared/collated.